Thermocouples for power generation are usually constructed with an n-type conductor, a p-type conductor and metal interconnects. The working of this thermocouple is based on the Seebeck effect. The Seebeck effect is illustrated in FIG. 1. The free electrons in the n-type conductor 101 move faster at the hot side than at the cold side. It is therefore more likely that an electron moves from the hot-side to the cold-side than reverse. This generates a flow of electrons from hot to cold, indicated generally by arrows 111. The same is true for the free holes in the p-type conductor 102: A flow of holes from hot to cold is indicated generally by arrows 112. For example, heat may be provided as schematically illustrated by arrows 104 to increase the temperature of heated surface 105. Heat may be removed from the system as illustrated schematically at arrows 106 to decrease the temperature of cold surface 107. Conductor 108 may conduct electricity between the n-type conductor 101 and the p-type conductor 102. Conductor 109 may conduct electricity between the n-type conductor 101 and a load 103, and conductor 110 may conduct electricity between the p-type conductor 102 and the load 103. This way, an electric current along the direction of arrows 113 may be generated, and/or an electric voltage may be generated.
Edwards, H.; Debord, J.; Tran, T.; Freeman, D.; Maggio, K., “Performance metrics for thermoelectric energy harvesting studied using a novel planar 65 nm silicon CMOS-based thermopile,” Sensors, 2013 IEEE, vol., no., pp. 1,4, 3-6 Nov. 2013, discloses thermocouples placed in series to obtain a higher output voltage.
To get the best conversion from heat flow to electrical power the system may be configured such that the electrical resistance of the n-/p-conductors is low but the thermal resistance is high. The most widely used thermoelectric materials are alloys of Bi2Te3 and Sb2Te3. The thermal conductance of these materials is lower than that of silicon. However, silicon has several advantages such us: cheaper to process, easier to integrate on ICs, and smaller structures can be generated.